X-ray absorption spectroscopic study on the electronic structure of Li(1)(-)(x)()CoPO(4) electrodes as 4.8 V positive electrodes for rechargeable lithium ion batteries

Changes in the electronic structure of olivine Li(1-x)CoPO(4), 4.8 V positive electrode material for lithium ion batteries, were investigated using the X-ray absorption spectroscopy (XAS) technique. The threshold energy in the Co K-edge increased with electrochemical Li removal, indicating the oxidation of cobalt ions due to charge compensation. Moreover, P and O K-edge XAS showed a slight shift in threshold energy with Li removal. Although it is generally believed that the electrons of PO(4) polyanion do not contribute to the oxidation process, present experimental results indicate changes in the electronic structure around PO(4) units. Such results would be interpreted by the idea of the hybridization effect between the Co 3d and O 2p orbitals and of the polarization effect introduced by Li ions.     

Enzymatic transformation of bacterial polyhydroxyalkanoates into repolymerizable oligomers directed towards chemical recycling

The enzymatic transformation into an oligomer was carried out with the objective of developing the chemical recycling of bacterial polyesters. Poly(R-3-hydroxyalkanoate)s (PHAs), such as poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyhexanoate)] and poly[(R-3-hydroxybutyrate)-co-12%(R-3-hydroxyvalerate)], were degraded by granulated Candida antarctica lipase B immobilized on hydrophilic silica (lipase GCA) in a diluted organic solvent at 70 degrees C. The degradation products were cyclic oligomers having a molecular weight of a few hundreds. The obtained cyclic oligomer was readily repolymerized by the same lipase (lipase GCA) to produce the corresponding polyester in a concentrated solution. The cyclic oligomer was copolymerized with epsilon-caprolactone using lipase to produce the corresponding terpolymers having an Mw of 21,000. This is the first example of the enzymatic chemical recycling of bacterial PHAs using lipase. Poly(R-3-hydroxybutyrate) [P(3HB)] was also degraded into the linear-type R-3HB monomer to trimer by P(3HB)-depolymerase (PHBDP) in phosphate buffer at 37 degrees C. The degradation using PHBDP required a longer reaction time compared with the lipase-catalyzed degradation in organic solvent. The monomer composition of the oligomer depended on the origin of the PHBDP. The R-3HB monomer was predominately produced by PHBDP from Pseudomonas stutzeri, while the R-3HB dimer was produced by PHBDP from Alcaligenes faecalis T1. Repolymerization of these oligomers by lipase in concentrated organic solvent produced a relatively low-molecular-weight P(3HB) (e.g., Mw=2,000). Degradation of P(3HB) by lipase in organic solvent into repolymerizable cyclic oligomer and degradation of P(3HB) by PHBDP in buffer into hydroxy acid type R-3HB dimer.     

A concise route to (+)-lactacystin

A facile chromatography-free route to Kang's intermediate for the synthesis of (+)-lactacystin, a potent proteasome inhibitor, has been developed starting with Brown's asymmetric crotylation of tert-butyl 5-formyl-2,2-dimethyl-1,3-dioxan-5-ylcarbamate, easily available from 2-amino-2-(hydroxymethyl)propane-1,3-diol (Tris).     

Age-dependent plasticity in the superior temporal sulcus in deaf humans: a functional MRI study

Background  

Sign-language comprehension activates the auditory cortex in deaf subjects. It is not known whether this functional plasticity in the temporal cortex is age dependent. We conducted functional magnetic-resonance imaging in six deaf signers who lost their hearing before the age of 2 years, five deaf signers who were >5 years of age at the time of hearing loss and six signers with normal hearing. The task was sentence comprehension in Japanese sign language.     

An efficient solid‐state polycondensation method for synthesizing stereocomplexed poly(lactic acid)s with high molecular weight

Simultaneous solid‐state polycondensation (SSP) of the powdery prepolymers of poly(L ‐lactic acid) (PLLA) and poly(D ‐lactic acid) (PDLA) can produce entire stereocomplexed poly(lactic acid)s (sc‐PLA) with high molecular weight and can be an alternative synthetic route to sc‐PLA. Ordinary melt polycondensations of L ‐ and D ‐lactic acids gave the PLLA and PDLA prepolymers having medium molecular weight which were pulverized for blending in 1:1 ratio. The resultant powder blends were then subjected to SSP at 130–160 °C for 30 h under a reduced pressure of 0.5 Torr. Some of the products thus obtained attained a molecular weight (M_w) as high as 200 kDa, consisting of stereoblock copolymer of PLLA and PDLA. A small amount of the stereocomplex should be formed in the boundaries of the partially melted PLLA and PDLA where the hetero‐chain connection is induced to generate the blocky components. The resultant SSP products showed predominant stereocomplexation after their melt‐processing in the presence of the stereoblock components in spite of containing a small amount of racemic sequences in the homo‐chiral PLLA and PDLA chains. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3714–3722, 2008     

Polarized Raman spectroscopic study of relaxed high density amorphous ices under pressure

We have made high density amorphous ice (HDA) by the pressure-induced amorphization of hexagonal ice at 77 K and measured the volume change on isobaric heating in a pressure range between 0.1 and 1.5 GPa. The volume of HDA on heating below ～0.35?GPa increases, while the volume of HDA on heating above ～0.35?GPa decreases. The polarized OH-stretching Raman spectra of the relaxed HDAs are compared with that of the unannealed HDA. The relaxed HDAs are prepared at 0.2 GPa at 130 K and 1.5 GPa at 160 K. It is found that the relatively strong totally symmetric OH-stretching vibration mode around 3100?cm(-1) exists in the depolarized reduced Raman spectrum χ(VH)(") of the unannealed HDA and that its intensity rapidly decreases by relaxation. The χ(VH)(") profiles of the relaxed HDA are similar to those of liquid water. These results indicate that the HDA reaches a nearly equilibrium state by annealing and the intrinsic state of HDA relates to a liquid state. The pressure-volume curve of the relaxed HDA at 140 K seems to be smooth in the pressure range below 1.5 GPa.     

Carbon sources of natural cyanamide in Vicia villosa subsp. varia

The 13C labels of [13C]carbon dioxide and D-[13C?]glucose were incorporated into cyanamide (NH?CN) when they were administered to Vicia villosa subsp. varia shoots. In contrast, the administration of sodium [2,3-13C?]pyruvate did not affect the relative area of the [M + 1]+ ion of cyanamide in the gas chromatography-mass spectrometry analysis. [2,3-13C?]pyruvate was incorporated into organic acids that are part of the citric acid cycle, such as succinate and fumarate, confirming that the shoots absorbed and metabolised it. These observations demonstrated that the carbon atom of cyanamide is derived from any of the carbohydrates that are present upstream of pyruvate in the metabolic pathway.     

Modular Synthesis of Polybenzo[b]silole Compounds for Hole‐Blocking Material in Phosphorescent Organic Light Emitting Diodes

A diversity‐oriented synthetic strategy allowed us to design a series of conjugated molecules containing multiple benzosilole units that can be utilized as efficient hole‐blocking materials for phosphorescent organic light emitting diodes (OLEDs). Some of these compounds showed a performance surpassing that of the current standard, bathocuproine. The new compounds were easily synthesized in a modular fashion from a previously reported 3‐stannyl benzosilole building unit. Studies on the properties of these compounds in solution and in the solid state indicate that they possess high electron affinity, high ionization potential, and form stable amorphous films that show high electron‐drift mobility. The correlation between their molecular properties and the efficiency of the OLED device performance is also investigated.